A valve such as a barrel valve is a flow control device used to manage a flow of fluid through a section of pipe. The typical barrel valve includes, among other things, a hollow barrel-shaped housing and a rotatable shaft having a channel passing therethrough. An upper portion of the rotatable shaft is coupled to an actuator.
To open the valve, the actuator moves the rotatable shaft until the channel is aligned with an inlet and an outlet in the housing. In this orientation, the valve permits the fluid to flow freely through the valve. To close the valve, the actuator moves the rotatable shaft until the channel is misaligned with respect to the inlet and outlet in the housing such that the rotatable shaft impedes flow between the inlet and outlet ports of the housing. To meter fluid flow through the valve, the actuator moves the rotatable shaft until the channel is partially aligned with the inlet and outlet in the housing. With the valve generally positioned somewhere between the fully open and closed positions, the valve partially permits or meters the fluid flowing through the valve.
To ensure that leakage of the fluid is reduced or, preferably, eliminated when the barrel valve is at or in between the open and closed positions, the barrel valve generally includes one or more seals. In a conventional barrel valve, at least one of these seals is interposed between mating members of the housing, between the housing and the rotatable shaft, and the like to ensure that the fluid does not undesirably escape from the valve.
To promote a good seal, the seal must maintain contact with adjacent structures which, in this case, are the housing and the rotatable shaft. The contact requirement is often accomplished using a variety of different biasing devices and methods. For example, supplemental springs are often coupled to or incorporated in the seal to provide a tensile force. The tensile force expands or elongates the seal such that opposing ends of the seal are biased against the housing and rotatable shaft. Alternatively, clamps are wrapped around the seal and used to provide a compressive force. Like the tensile force, the compressive force also expands or elongates the seal such that opposing ends are pushed against the housing and the rotatable shaft. By forcibly biasing the ends toward mating structures, the sealing relationship is formed, the integrity of the seal is maintained, and leakage is prevented.
Unfortunately, the use of springs and clamps to maintain a seal between adjacent structures has significant drawbacks. For example, typical springs and clamps are constructed of metal. Because metal is relatively expensive compared to polymers and other typical valve construction materials, the springs and clamps add to the overall cost of the valve. Metals can also corrode when exposed to various fluids. This leads to the need for frequent inspections and, potentially, the costly and time-consuming replacement of the metal parts.
In addition to being costly and subject to premature failure, the springs and clamps all too often require that additional steps be undertaken during assembly of the valve. For example, the spring has to be attached to the seal and the clamp must be wrapped around the seal. These manufacturing steps add to the overall cost of the valve. Moreover, the assembly equipment required to construct a valve that includes springs and clamps must be more advanced or sophisticated to handle the extra component. In addition, during operation, in some cases the springs and clamps undesirably elevate operating torque. Therefore, a larger and more costly actuator must be used to move the rotatable shaft and operate the valve.
In other flow control valves, o-rings are situated between the adjacent structures. The o-rings rely on an interference fit between the housing and rotatable shaft to prevent leakage. By forcing the o-rings into the space between adjacent structures, the o-rings are generally held in compression. The compressive force causes the o-ring to push outwardly toward the adjacent structure and, as a result, the o-ring promotes a tight seal.
Like the springs and clamps, the o-rings also have significant drawbacks. For example, the o-rings rely upon an interference fit to prevent leakage. The interference fit places high compressive loads on the seal. These high compressive loads make the seal more prone to failure. Moreover, if tolerances of the o-ring or adjacent structure are off, the seal may undesirably permit leakage.